The definition of mince is to cut into very small pieces. This term means the smallest possible pieces; smaller than dice or chop, but not pureed. To do this, you need a very sharp knife and a steady hand. Practice will make perfect.
Examples of Mincing
The garlic should be minced so the flavor is evenly distributed throughout the stir fry.
Mincing food means cutting into pieces about 1/8" or 1/16" in diameter. This is the smallest size without cutting food into a pulp or puree. Use a very sharp knife when mincing. You can cut food into pieces about 1/2", then, using a chef's knife, run the knife over the pieces, occasionally stopping to move the food around with your fingers, until the size is uniform.
Used for Seasoning
Most foods that are minced are used for seasoning, such as onions, garlic, and celery. You can also mince foods in a food processor or blender, but it can be difficult to stop before the food is pureed. Practice mincing until you are comfortable with chopping food into small and even pieces.
Some food is minced because it will be evenly distributed in a recipe, such as onions in a stew. Other foods are minced because their flavor will be stronger, such as garlic. Whole cloves or sliced garlic will be milder than garlic that is crushed or minced. Follow the instructions in recipes carefully.